Linear Assembly For Full Unrolled If-Then-Else Code - Texas Instruments TMS320C6000 Programmer's Manual

Loop Unrolling
Example 6–54. Linear Assembly for Full Unrolled If-Then-Else Code
.global
_unrolled_if_then:
.reg cword, mask, theta, ifi, ifi1, a, ai, ai1, cntr
.reg cdi, cdi1, sumi, sumi1, sum
MV A4,a
MV B4,cword
MV A6,mask
MV B6,theta
MVK 16,cntr
ZERO sumi
ZERO sumi1
LOOP: .trip 32
AND .L1X cword,mask,cdi ; cdi = codeword & maski
[cdi] MVK .S1 1,cdi
CMPEQ .L1X theta,cdi,ifi
LDH .D1 *a++,ai
[ifi] ADD .L1 sumi,ai,sumi
[!ifi] SUB .D1 sumi,ai,sumi
SHL .S1 mask,1,mask
AND .L2X cword,mask,cdi1 ; cdi+1 = codeword & maski+1
[cdi1] MVK .S2 1,cdi1
CMPEQ .L2 theta,cdi1,ifi1 ; (theta == !(!(cdi+1)))
LDH .D1 *a++,ai1
[ifi1] ADD .L2 sumi1,ai1,sumi1 ; sum += a[i+1]
[!ifi1] SUB .D2 sumi1,ai1,sumi1 ; sum –= a[i+1]
SHL .S1 mask,1,mask
[cntr] ADD .D2 –1,cntr,cntr
[cntr] B .S2 LOOP
ADD sumi,sumi1,sum
.return sum
.endproc
6-98
_unrolled_if_then
.cproc a, cword, mask, theta
; C callable register for 1st operand
; C callable register for 2nd operand
; C callable register for 3rd operand
; C callable register for 4th operand
; cntr = 32/2
; sumi = 0
; sumi+1 = 0
; !(!(cdi))
; (theta == !(!(cdi)))
; a[i]
; sum += a[i]
; sum –= a[i]
; maski+1 = maski << 1;
; !(!(cdi+1))
; a[i+1]
; maski = maski+1 << 1;
; decrement counter
; for LOOP
; Add sumi and sumi+1 for ret value